This invention relates to laminated packaging materials for foodstuffs. More particularly, it relates to a laminated material suitable for use in flexible containers for foods such as potato chips, corn chips, and the like.
Flexible walled pouches, bags and similar containers have been used with satisfactory results, and to an increasing extent, in the packaging of products such as potato chips and corn chips where it is essential that the freshness of the product be maintained for a number of months. Generally, such containers are prepared from multi-layered laminated packaging materials whose layers comprise polyolefin resin films and metallic foil. The packaging materials may have from 2 to 8 or more discrete layers, of which one or more layers may consist of adhesive material.
U.S. Pat. No. 3,616,190 discloses a laminated packaging material comprising--in order from the outer surface to the inner surface--cellophane, polyethylene, aluminum foil and heat-sealable polyethylene. The cellophane functions both as an outer surface and as a decorative surface, the decorative design being printed in reverse on the inner side of the cellophane sheet.
U.S. Pat. No. 4,096,309 discloses a laminate comprising a non-woven outer sheet of spun-bonded polymer such as polyethylene, polypropylene or polyester. The next adjacent layer can be a polyolefin film such as polyethylene or polypropylene. The next adjacent layer is a metallic foil and the innermost layer is a heat-sealable polyolefin such as polyethylene or polypropylene. As an outer surface layer, there is preferably provided a face ply of a smooth, nonporous material, such as kraft paper.
U.S. Pat. No. 4,190,477 discloses a laminate of (1) polyester or nylon, (2) metallic foil, (3) extrusion-grade propylene polymer or copolymer and (4) a sealant layer of polypropylene, polyethylene or ethylene vinyl acetate.
In the packaging of foodstuffs such as potato chips, corn chips, and the like, the packages are generally imprinted on the outermost layer of a laminate from which the package is made. When the outermost layer is transparent, the printing thereon is often difficult to discern, particularly, if the package contents do not provide sufficient contrast between the lettering and its background. In addition, one or more layers of metal foil are typically included in the laminate materials from which such packages are formed. It is often difficult to obtain a proper bond between the foil and the other layers of the laminate. It would therefore be desirable to provide a packaging material in which the layer underlying the transparent outer layer is pigmented and serves to provide a strong bond to a subsequent layer of metal foil.